Exchange 2007 CAS server redundancy and high availability.

I have an Exhange 2007 2 node CCR with one CAS HUB Transport server.I need to setup a 2nd CAS HUB Transport Server for redundancy and high availability.
With Client Access--You can use NLB or a third-party hardware-based NLB device for Client Access server high availability. Does the NLB or DNS  round robin have to be on the same subnet ?
How would you setup the Exchange Exchange CAS Server NLB or DNS round robin, what are the pros and cons?
cap7Asked:
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DocCan11Connect With a Mentor Commented:
This is actually a combination of questions.. First lets deal with the hub.. no they do not have to be on the same IP subnet BUT (and this is a BIG but) they MUST be in the same AD site if you want them to provide fault tolerance for each other.. Exchange 2007 only allows a hub to communicate with Mailbox servers in the SAME AD site.. so be careful with this..

DNS round robinning just returns all records that match a query regardless of where they are.

NLB is far superior to DNS becuase DNS will continue to send clients to the down node and only after they timeout will they connect to the up node.. with NLB it will occur automatically..

Here is an article that covers it..

http://technet.microsoft.com/en-us/library/bb742455.aspx

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cap7Author Commented:
Does the NLB needs a file witness share ?
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DocCan11Commented:
no.. you only need a witness share when you are deciding to implement CCR and that only protects a Mailbox server role
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